The Vault, a coffee shop and community art space in Valley City, N.D., generated buzz recently for its somewhat unusual business model: the honor system.

The shop, which opened in October 2013, serves coffee, snacks, baked goods and soup. Customers select what they'd like to eat and drink and then put cash and checks in a drop box or use a credit card scanner to pay. No staff person takes customer money. It all runs on trust.

It may seem like a risky business choice, but owners David and Kimberly Brekke have averaged 15% more than their asking prices, according to the company's website. "We do see theft from teenagers who occasionally need talking to," reads a statement on the website, but "among adults the rate of theft is nearly zero."

While the model the Brekkes are using may work in Valley City, the honor system requires just the right set of circumstances, so don't expect all your local retailers to suddenly dispense with cashiers and security.

"It's more likely to work in a small town than a big city because reputation is at play," said Joshua Green, a psychology professor at Harvard University. "If people see you taking without giving, that's more likely to have repercussions," he said.

Michael Cunningham, a psychologist in the communication department at the University of Louisville, told USA TODAY Network that an honor system requires two circumstances.

First, "people have a commitment to their personal honor" and value having a good reputation, which he says applies to a vast majority of people. And second, those people need to feel that they are in an "equitable relationship" with the other party, meaning that they don't feel taken advantage of or exploited.

"In a coffee shop, if you feel that the prices are reasonable, and the staff is really trying, then many people will follow through on the honor system," he said.

When asked why people might pay more than they owe, as The Vault owners claim, Cunningham said that's probably because they like that the owners trust them.

"Sometimes people are more generous because they appreciate the compliment of the trust," Cunningham said.

And perhaps Valley City is just part of an uptick in honesty across the country.

In a survey conducted by Honest Tea, a beverage company owned by CocaCola, 95% of people in 60 locations in 50 states, paid a dollar before taking a drink from an honor-system street display. That's up from 92% last year.